Cathode ray tube



NOV. 5, 1940. I SITEUDEL ET AL 2,220,181

CATHODE- RAY TUBE Filed June 22, 1957 INVENTORS PEER/MRO srzuoa .40264/. JOIlANNESSO/V A'l'TRNEY Patented Nov. 5, 1940 PATENT OFFICE2,220,181 GATHODE RAY TUBE Eberhard Steudel and Jurg Johannesson,Berlin, Germany, assignors to Allgemeine Elektricitats Gesellschaft,Berlin, Germany, a'corporation of Germany Application June 22, 1937,Serial No. 149,576 In Germany June 26, 1936 1 Claim.

The invention relates broadly to apparatus embodying the use of acathode ray, and more particularly to a cathode ray tube structure whichis particularly adaptable to use in television.

The life of a Braun or cathode ray tube depends largely upon the life ofthe filament of the cathode. Once the latter has blown or has beenburned through, the entire tube becomes unserviceabie. Braun tube havinga long life is created by using a photo-cathode for the cathode. Thespot, as known in the art, may be produced by imaging the cathode or astopper or diaphragm mounted anteriorly thereof. Illumination of thephotocathode may be produced either by means of naural light or else byan artificial light source. For this purpose will sufiice an ordinaryglowlamp, say, a pocket lamp which may be readily replaced in case itblows, and with which, under certain circumstances, the photo-cathodesof several Braun tubes may be illuminated simultaneously.

One exemplified embodiment of the Braun tube here disclosed is shown inthe appended drawing. The Braun tube I is furnished with a photoelectriccathode 2 which is illuminated by the aid of a light source 3 and,optionally, an interposed lens 4. If the photocathode is of thetransparent or translucent kind, illumination could be also posterior.The electrons which are released from 2 are projected by means of anaccelerator cylinder 5 upon a fluorescent screen 6. The potential fieldbetween 2 and 5 is in the shape of an electric lens. If desired,additional electric or magnetic lenses could be provided. I and 8 arepairs of deflector plates known in the earlier art, and of these or bothmay be replaced by pairs of deflector coils. In addition, diaphragms,stops and electron lenses may be provided for the purpose of insuringlimitation or stopper (focusing) eliects upon the beam or pencil and forintensity modulation.

Another embodiment of the basic idea of this invention consists indisposing between light source 3 and photo-cathode 2 a replaceable orremovable pattern or vignette 9 by the aid. of which a spot of specialshape may be projected According to the present invention, a

upon the photo-cathode, say a line, which, when the cathode is imagedupon the luminescent screen will produce a spot upon the screen ofcorresponding form. This may prove advantageous for certain purposes,say, for sound-film work. It is thus feasible to render one and the sametube useful for several kinds of work, whereas in the past special waysand means had to be adopted in the interior of the tube for the purposeof producing a luminous line of the sort required for sound-film work(cylinder lenses or equivalent means).

According to this invention also an intensity modulated source of lightcould be employed. It is thus possible, for instance, in televisionequip- 15 ment, to insure intensity modulation and line modulation (orline scan) in two distinct tubes so that mutual interference of the twocontrol or modulation actions will be eliminated to a large extent.Moreover, each of these tubes may 20 be designed in a way so that itwill give greatest satisfaction in the particular kind of Work for whichit is intended. The light source, in this instance, may consist eitherof another cathoderay tube (and if desired, the latter could also be 25furnished with a photo-electric cathode and distinct light source justlike the tube of the invention), or else a glow-tube, Kerr cell or anyother intensity controlled source of light.

What is claimed is:

A cathode ray system comprising a cathode ray tube having an envelopeincluding photo-electric cathode means for releasing electrons, meansfor concentrating said electrons into a beam formation, means foraccelerating said electron beam formation, and a screen adapted to giveofi' light in response to the impingement of said cathode ray beamthereon, a source of light positioned external to said tube envelope,and removable pattern means positioned between said source of light andsaid photo-electric cathode whereby the light from said light sourcepassing through said removable means and impinging on said photoelectriccathode has a definite predeterminable pattern.

EBE-RHARD STEUDEL. J URG J OHANNESSON.

